Movement and distribution of adult Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) in stored wheat in response to temperature gradients, dockage, and moisture differences

The movement and distribution of adult Cryptolestes ferrugineus were determined in 100×100×1000 mm wheat columns with or without 5 °C/m temperature gradients (from 27.5±0.2 to 32.5±0.2 °C or at 27.5±0.2 °C) under: (1) 5% and 10% uniform dockage (14.5±0.2% moisture content (m.c.), wet basis); (2) half of the columns with 5% or 10% dockage and the other half without dockage; (3) 12.5%, 14.5% or 16.5% m.c. wheat without dockage; and (4) half of the columns with 12.5% or 14.5% m.c. wheat and the other half with 16.5% m.c. wheat.Adults introduced in the middle of the horizontal wheat columns with or without uniform dockage showed no bias in the direction of net displacement, with the distribution pattern gradually becoming more uniform when time increased from 1 to 144 h. In vertical columns with 0%, 5% and 10% uniform dockage, the adults preferred to move down in the first 24 h; however, they moved up after 24 h. Grain with a high percentage of dockage (10%) decreased beetle movement speed. A low percentage of dockage (5%) did not influence insect movement and distribution. Positive geotaxis was more important than the attraction of dockage.Adults responded to both temperature gradients and moisture differences in columns of wheat with temperature gradients and moisture content differences. The response was different at different moisture conditions. Adults were more sensitive to moisture differences and moved faster in 12.5% m.c. wheat than in 14.5% m.c. wheat. Adults stayed in warmer sections in both high and low moisture grain. At different moisture conditions, adults changed their preference (e.g., preferred high moisture grain in dry grain, and preferred warmer temperature in damp grain).     

Segregation in stored grain bulks: Kinematics,dynamics, mechanisms,and minimization – A review

Stored grain is a mixture of grain kernels, dockage, and foreign materials. During the handling of grain bulks, segregation is a natural tendency of the grain mixture components differing in some properties such as size, shape, density, particle surface roughness, electrostatic charge, chemical affinities and stability, and/or thermal stability. Segregation causes many grain storage problems such as uneven distribution of airflow rate during grain drying and aeration. Due to the importance of uniform distribution of dockage and foreign material inside stored grain bins, minimization of segregation during grain storage and handling is necessary. This review characterized the kinematics and dynamics of segregation during grain loading and unloading, classified segregation mechanisms of grain bulks to four categories (trajectory, fluidization, shifting, and impact), identified the factors influencing the segregation, analyzed the relationship between airflow resistance and segregation, summarized the studies on the mathematical modeling of segregation, and provided the suggestions on the minimization of segregation. Mixtures consisting of multiple components and broad particle size distributions pose even greater difficulties in predicting segregation. Among these difficulties, the impediment is that there are few studies available to identify the segregation during grain handling. Therefore, conducting further studies on the segregation of grain mixtures in the future would be helpful.     

Hemp (Cannabis sativa) seed for reproduction of stored-product insects

Hemp, or industrial hemp (Cannabis sativa), is a high value alternative crop that has seen increases in production in Canada since commercial production was legalized in 1998. Insect infestation of stored hemp seed may result in loss of quality and value. There are few published studies on the ability of insects to survive and reproduce on hemp seed. Reproduction of eleven stored-product insects on hemp seed at different moisture contents with, or without dockage, was studied. Insects were introduced into 15 g of hemp seed at two initial moisture contents (dry, 9% m.c. or damp, 15% m.c.), two dockage levels (dockage-free or dockage, 15%), and held at 30°C and 60–70% r.h. Five replicates of each treatment for each species were used. For beetles, twenty unsexed adults were used, for Ephestia kuehniella (Mediterranean flour moth), twenty eggs were used. For the beetles, live and dead adults were counted after 3, 5, 7 and 9 weeks, for the moth, adults were counted after 12.5 weeks. After counting, only live adults were returned to the hemp seed. The following beetle populations increased over the 9 weeks; Tribolium castaneum (red flour beetle), Lasioderma serricorne (cigarette beetle), Oryzaephilus surinamensis (sawtoothed grain beetle) and Trogoderma variabile (warehouse beetle). The following species did not increase their populations; Cryptolestes ferrugineus (rusty grain beetle), Rhyzopertha dominica (lesser grain borer), Sitophilus oryzae (rice weevil), Cryptolestes turcicus (flour mill beetle), Tribolium confusum (confused flour beetle), and Stegobium paniceum (drugstore beetle). For the beetles, higher dockage generally led to higher populations. The effect of moisture content was variable. Ephestia kuehniella produced adults on all treatments, with the dry treatment containing dockage performing the best.